Octopamine receptor subtypes and their modes of action

Octopamine receptor subclasses were first proposed to explain differences in the pharmacological profiles of a range of physiological responses to octopamine obtained in the extensor-tibiae neuromuscular preparation of the locust. Thus, OCTOPAMINE₁ receptors which inhibit an endogenous myogenic rhythm, increase intracellular calcium levels. Also OCTOPAMINE₂ receptors which modulate neuromuscular transmission in this preparation, increase the level of adenylate cyclase activity. The current status of this classification is reviewed by examining the pharmacology of responses to octopamine in a range of preparations. It is concluded that the distinction between OCTOPAMINE₁ and OCTOPAMINE₂ receptor types is still valid, but that OCTOPAMINE₂ receptors exhibit some tissue specific variations. Studies on a clonedDrosophila octopamine/tyramine (phenolamine) receptor are discussed and illustrate many of the difficulties presently encountered in making a definitive classification of octopamine receptors. These include the possibilities that single receptors may activate multiple second messenger systems and that different agonists may differentially couple the same receptor to different second messenger systems.     

The xylanase introns from Cryptococcus albidus are accurately spliced in transgenic tobacco plants

The xylanase gene from Cryptococcus albidus contains seven introns. Genomic and cDNA clones under the control of the CaMV 35S promoter were transferred into tobacco plants using Agrobacterium-mediated cell transformation. The genes were transcribed and the mRNAs were amplified by the polymerase chain reaction using primers on each side of the intron region. About 90% of the amplification products from plants transformed with the genomic clone corresponded to the size of the pre-mRNA (1.2 kb) and 10% represented the spliced product (0.85 kb). The 0.85 kb fragment was cloned and sequenced and the result indicated that the introns from the xylanase gene were accurately spliced by the plant cells.     

Effects of population size and forest management on genetic diversity and structure of the tuberous orchid Orchis mascula

Due to societal changes and altered demands for firewood, the traditional forest management of coppicing has been largely abandoned. As a result, many forest herbs that are specifically adapted to regular opening of the canopy, have suffered significant declines in abundance, and the remaining populations of these species often tend to be small and isolated. Reduced population sizes and pronounced spatial isolation may cause loss of within-population genetic diversity and increased between-population differentiation through random genetic drift and inbreeding. In this study, we investigated genetic diversity and genetic structure of 15 populations of the food-deceptive orchid Orchis mascula using AFLP markers. Within-population genetic diversity significantly increased with increasing population size, indicating genetic impoverishment in small populations. Genetic differentiation, on the other hand, was rather low (Φ_ST = 0.083) and there was no significant relationship between genetic and geographic distances, suggesting substantial gene flow within the study area. However, strong differences in levels of within-population diversity and among-population differentiation were found for populations located in forests that have been regularly coppiced and populations found in forests that were neglected for more than 50 years and that were totally overgrown by shrubs. Our data thus indicate that a lack of coppicing leads to decreased genetic diversity and increased differentiation in this orchid species, most likely as a result of genetic drift following demographic bottlenecks. From a conservation point of view, this study combined with previous results on the demography of O. mascula in relation to forest management illustrates the importance of coppicing in maintaining viable populations of forest herbs in the long-term.     

Sequence analysis of cohesive ends of the actinophage RP3 genome and construction of a transducible shuttle vector

Abstract The sequence of the cohesive ends of actinophage RP3 DNA has been determined. As with all other phages of Gram-positive bacteria that have been studied sofar, RP3 DNA has 3'-protruding ends. A shuttle cosmid has been constructed containing this cos area which can be efficiently transduced by phage RP3 to host cells of Streptomyces rimosus .     

Neighbourhood effects on the risk of an unpalatable plant being grazed

Most studies on the importance of the neighbourhood on a plant's risk ofherbivory have focused on palatable plants and how they are protected byunpalatable neighbours. This study examined the grazing intensity of arelatively unpalatable shrub, Buxus sempervirens, indifferent neighbours. Exactly 2683 plants of Buxussempervirens (including 172 controls) were sampled in 12 enclosedpastures belonging to 4 sheep farms. The enclosures were grazed at 3 differentseasons (spring, summer and autumn). Plants were divided in 4 age/hight classes(first year, < 4 cm, 4–10 cm, 10–40cm) and into 8 neighbourhoods. The first of these wascharacterisedby the absence of any plants within a radius of 5 cm around theBuxus individual and the 7 others by the identity of thedominant species in contact with the Buxus plant. Theintensity of grazing on the neighbouring plants were also recorded. At the endof one year's monitoring, 26.2% of Buxus sempervirensplants had been grazed. The proportion of plants grazed was significantlyhigherin spring than in the other two seasons. It decreased with increasing plantage.It was higher in neighbourhoods that were intensively grazed than in those withlight grazing. The proportion grazed in the absence of a neighbour plant wasintermediate between the previous two. The probability of a plant of aninvadingspecies being grazed is influenced by factors other than its life-historytraits. Some neighbourhoods consisting of unpalatable plants facilitate theestablishment of Buxus sempervirens by protecting theyoungplants from grazing, whereas other highly palatable neighbourhoods are readilygrazed by sheep, thus indirectly increasing the proportion of Buxussempervirens that are grazed. The young and short (< 4cm in height) Buxus plants, which are lessrecognisable by sheep, are most sensitive to the impact of grazing.     

Detection of Naegleria fowleri cysts in environmental samples by using a DNA probe

Abstract In this study we tried to detect DNA Naegleria fowleri in artificially contaminated environmental samples, with or without sediments, containing 10⁴ cysts of this pathogenic amoeba. We used two assays to extract DNA from samples: first, direct DNA extraction, which gave positive results only for water samples without sediment; second, DNA extraction after sample incubation on agar plates, which allowed us to remove amoeba growing out of the sediments, and which gave positive results for all samples, even those initially with sediments (5, 500 or 500 mg). Thus, this molecular identification appears as a powerful tool to investigate N. fowleri growth in environmental samples.     

Genetic and biochemical evidence for involvement of HOTHEAD in the biosynthesis of long-chain α-,ω-dicarboxylic fatty acids and formation of extracellular matrix

In plants, extracellular matrix polymers built from polysaccharides and cuticular lipids have structural and protective functions. The cuticle is found to be ten times thinner in Arabidopsis thaliana (L.) Heynh than in many other plants, and there is evidence that it is unusual in having a high content of α-,ω-dicarboxylic fatty acids (FAs) in its polyesters. We designated the new organ fusion mutant hth-12 after it appeared to be allelic to adhesion of calyx edges (ace) and hothead (hth), upon molecular cloning of the gene by transposon tagging. This mutant is deficient in its ability to oxidize long-chain ω-hydroxy FAs to ω-oxo FAs, which results in leaf polyesters in decreased α-,ω-dicarboxylic FAs and increased ω-hydroxy FAs. These chemical phenotypes lead to disorder of the cuticle membrane structure in hth-12. ACE/HTH is a single-domain protein showing sequence similarity to long-chain FA ω-alcohol dehydrogenases from Candida species, and we hypothesize that it may catalyze the next step after cytochrome P450 FA ω-hydroxylases in the ω-oxidation pathway. We show that ACE/HTH is specifically expressed in epidermal cells. It appears very likely therefore that the changes in the amount of α-,ω-dicarboxylic FAs in hth-12 reflect the different composition of cuticular polyesters. The ACE/HTH gene is also expressed in root epidermal cells which do not form a polyester membrane on the exterior surface, thereby making it possible that the end products of the pathway, α-,ω-dicarboxylic FAs, are generally required for the cross-linking that ensures the integrity of the outer epidermal cell wall.     

Iron uptake regulation in Pseudomonas aeruginosa

The Pseudomonas genus belongs to the γ division of Proteobacteria and many species produce the characteristic yellow–green siderophore pyoverdine, and often a second siderophore, of lower affinity for iron. These bacteria are known for their ability to colonize different ecological niches and for their versatile metabolism. It is therefore not surprising that they are endowed with the capacity to take up exogenous xenosiderophores via different TonB-dependent receptors. Uptake of iron is controlled by the central regulator Fur, and via extracytoplasmic sigma factors or other types of regulators (two-component systems, AraC regulators). In this review the Fur regulon (experimentally proven and/or predicted) of P. aeruginosa will be presented. An interesting feature revealed by this analysis of Fur-regulated genes is the overlap between the iron and the sulfur regulons as well with the quorum sensing system.     

Effect of microspore stage and media on anther culture of peanut (Arachis hypogaea L.)

This study was designed to study the effects of stage of microspore development and culture medium on androgenic response in peanut (Arachis hypogaea L.). Anthers of various developmental stages were cultured for 7 days, then fixed and observed cytologically. Three sets of media, involving different basal media, growth regulators, sucrose levels and glutamine concentrations, were tested. In all experiments, the stage of development of the microspores at the time of culture was highly significant. The early uninucleate microspores stage was identified as producing the highest anther response rating. The effect of media was nonsignificant in all experiments. However, the stepwise modification of the media through the course of the study resulted in an almost 8 x increase in anther response rating. Numerically, the best media tested was N₆ basal medium with 1 mg 1^-1 NAA, 0.1 mg 1^-1 BA, 5.5% sucrose, and 3.5 g 1^-1 glutamine. While no haploids were obtained, four-nucleate cells were observed, indicating the potential in peanuts for an androgenic reponse.     

Two-stage culture for producing berberine by cell suspension and shoot cultures of <Emphasis Type="Italic">Berberis buxifolia</Emphasis> Lam

In vitro cultures of Berberis buxifolia were established using thidiazuron (4.5, 23 and 45 mM) or picloram (4 and 40 mM) as plant growth regulators for sustaining growth. For producing berberine, a two-stage culture was performed. In the first step, thidiazuron or picloram were used for biomass production followed by the production stage where benzylaminopurine (4.4 mM) was added as a plant growth regulator. Berberine yields (102 mg g⁻¹ DW) and in vitro shoot cultures (200 mg g⁻¹ DW) were significantly lower than those of whole plants in the field (416 mg g⁻¹ DW). The highest productivity (0.18 mg 1⁻¹ day⁻¹) was attained using picloram (either 4 on 40 mM) in the first stage for producing biomass.